This document discusses different types of variable capacitors and inductors. It describes that variable capacitors have capacitance that can be varied by rotating a shaft, and includes ganged and trimmer capacitors. Inductors are coils that produce a magnetic field opposing changes in current through the coil. Types of inductors include air core, iron core, and ferrite core inductors. The document also covers voltage ratings of capacitors, tolerance of capacitors, and mutual inductance between two coils.